Skid steer loaders are work vehicles that include four wheels rotatably mounted to a frame, an engine mounted on the frame and connected by a transmission to rotate at least two wheels, a cab compartment mounted on the frame that includes a seat for an operator, manual controls and a display panel disposed in the cab compartment, a boom assembly rotatably mounted on the frame and connected to a pair of hydraulic boom cylinders for moving the boom assembly, and an implement assembly connected to the boom assembly. Typically, one or more hydraulic cylinders are used to manipulate the implement assembly. Preferably, the implement assembly is a bucket assembly, wherein the implement is a bucket and a pair of hydraulic bucket cylinders is used to move the bucket assembly. Other types of work vehicles that are similar to skid steer loaders include tractors and bulldozers.
To operate the hydraulic boom cylinders and the hydraulic bucket cylinders, an operator in the cab manipulates either hand or foot controls. The skid steer loader, or similar work vehicle, includes an electronic control circuit system that includes an onboard computer, microprocessor, or controller. For the purposes of this disclosure, a computer, microprocessor, or controller are considered to be equivalent and interchangeable elements. The onboard computer operates solenoids of electrohydraulic valves that activate the hydraulic boom and bucket cylinders. To ensure the safe operation of the work vehicle, the electronic control system can be configured to include a safety feature that enables the operation of the electrohydraulic solenoid valves of the hydraulic cylinders only when a safety switch circuit is properly activated. One such electrical circuit forming the controller of a boom solenoid valve is disclosed in U.S. Pat. Nos. 4,856,612 and 4,871,044 to Clevenger, Jr. et al. and to Strrosser et al. respectively, both of which are incorporated herein in their entirely by reference. In the electrical circuit of this controller, there is a built in safety feature wherein the controller cannot operate the boom solenoid valve unless both the belt switch and a seat switch were activated by the simultaneous conditions of (a) having the seat belt restraint mechanism engaged and (b) having an operator sitting in the operator's seat.
U.S. Patent Application Publication U.S. 2001/0007087 A1 to Brandt et al., which is also incorporated herein by reference for all it discloses, teaches a computer based control system for a skid steer loader that includes a computer receiving inputs from a control panel, various sensors, hand grip and foot pedal inputs, and a seat bar sensor. The computer generates outputs to hydraulic actuators and associated valves, and to electromechanical devices.
The prior work vehicles have several drawbacks. First, it is desirable to permit an operator to select enablement of either hand or foot controls for manipulating the boom assembly and the bucket assembly. In addition, because the boom assembly and the bucket assembly are manually controlled separately, the operator can mistakenly dump out the contents of the bucket inadvertently. In some cases, such as when operating a fork lift, it may be an advantage to manipulate the boom assembly while maintaining a constant angular bucket position (i.e. horizontal) of a fork lift work implement to the ground or to the work vehicle. Therefore, it would be beneficial to provide an electronic control system for a work vehicle that includes a multi-mode self-leveling bucket option for maintaining a constant angular bucket position of the bucket to the ground, to the work vehicle, or to some returnable position of advantage.
The present invention endeavors to provide an improved electronic control system for a work vehicle, or like machine, having a boom assembly and a work implement assembly connected to the boom assembly so that the improved electronic control system of the present invention maintains the benefits of the prior electronic control systems while overcoming the drawbacks of these prior control systems.
Accordingly, one object of the present invention is to overcome the disadvantages of the prior art electronic control systems for work vehicles and like machines.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that includes a safety switch to prevent enablement of the solenoids of the boom assembly and the bucket assembly unless an operator is sitting in the operator's seat and/or the seat belt restraint device has been properly secured.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that includes a multi-mode self-leveling bucket option for maintaining a constant angular bucket position of the bucket to the ground, to the work vehicle, or to some desired retrievable position of advantage.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that permits the selection and enablement of either hand or foot controls to manipulate the boom assembly and the implement assembly.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that is practical and cost effective to manufacture.
Another object of the present invention is to provide an electronic control system for work vehicles, and like machines, that is both durable and reliable.
Of course, while the electronic control system for work vehicles, and like machines, will be described for use in skid steer loaders and like machines, another object of the present invention is to provide an electronic control system for a machine having a boom assembly and an implement assembly connected to the boom assembly, wherein the machine can be a self-propelled machine or a stationary machine.